Access for medical procedures has always been an important aspect for minimally invasive percutaneous interventional procedures, including endovascular procedures that require access to the venous or arterial system, or procedures that simply require access to an interior body cavity. In general, it is desirable to make the smallest incision point with the shortest tissue contact time when entering the body. Small incisions and short tissue contact time generally lead to improved patient outcomes, less complications, and less trauma to the vessels or organs being accessed, as well as to the skin and tissue through which the access point is created.
Innovations in percutaneous procedures continue and new devices and device concepts are introduced continually. In recent years, there has for example been high interest in placing structural elements (such as heart valves, heart valve repair devices, occluders (PFO, ASD, appendage, etc), grafts, electrical stimulators, leads, etc) percutaneously. One issue that physicians face is that these are often very large devices that require very large sheaths to deliver them to the intended site within the body. Sheath sizes of 16-24 F (0.21″-0.315″) are commonly used for these procedures. As a result, access site trauma has been increasing; often resulting in vessel damage, excessive bleeding, increased case time, increased risk of infection, and increased hospitalization time.
To reduce access trauma, physicians try to use the smallest devices possible and place the smallest sheath size. This can be problematic, however, if during the procedure they discover a larger device is needed. This leads to a need to upsize the sheath, which is a lengthy procedure and leads to increased risk to the patient. Companies have tried to respond to these challenges by designing the smallest devices possible.
Some companies, such as Edwards Lifesciences and Terumo, have offered expandable sheaths that can be expanded within the body and thus do not require removal to upsize. The Edwards device is a slit sheath that overlaps radially and the Terumo device expands by inflating a balloon in the sheath. Both of these designs still have considerable problems.
A slit sheath design is problematic because increasing the perimeter of the sheath by moving the overlapping section still does not increase the diameter of the sheath significantly. This is due to the ratio of perimeter to area in a circle. Increasing the perimeter of a circle increases the area by a much smaller amount. Thus these known devices only increase in size by approximately 2 F (0.026″ diameter). Also, such a design contains sharp edges that can damage a vessel.
The balloon expandable design expands to a greater degree than the slit design, but has other drawbacks including added steps and complexity to use, minimal control over expansion, potential trauma due to the large expansion force when the balloon is inflated, and the inability to recoil during use, thus resulting in continual compression of tissue during a procedure.
Both slit sheath and balloon expandable designs also have a major drawback in that they are not ‘regionally’ expansive along the length of the sheath, but instead the entire length of the sheath needs to be expanded or not expanded. Further, these sheaths are not very recoverable when not passing a large device through them—thus not ‘retractable’ to the original small size. These issues contribute to vascular trauma.
There is a need in the art for an improved introducer sheath and related methods.